Under-Eye CirclesDo you suffer from chronic dark under-eye circles? If you've tried everything from getting more rest, to changing your diet to moisturizing, and your dark circles won't go away, pay a visit to a doctor. The circles could indicate that you're suffering from allergies that you aren't aware of.

"Dark circles are what we refer to in the allergy world as allergic shiners, because they basically look like you've been hit right under the eye," allergist Dr. Marc Meth says.

Allergic shiners are caused by blood pooling under the eyes as the result of nasal and sinus congestion, Dr. Meth explains. You can prevent them through the use of medication, by avoiding common allergens or by having an allergy shot.

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Fading creams, laser treatments and chemical peels are all viable options to eliminate dark circles that are not caused by allergies. A good at-home tip Dr. Ordon offers is soaking chamomile or green tea bags in cold water and placing them on your eyelids for 15 minutes. "I like putting them in my freezer, because they thaw pretty quickly," he adds. "That will help dark circles under your eyes."

Hypothyroidism occurs when the thyroid gland, which produces and stores hormones that help regulate heart rate, blood pressure, body temperature and metabolism does not produce enough thyroid hormone. This causes the metabolism and other bodily functions, such as hair growth, to slow down. In addition to brittle hair, other symptoms of hypothyroidism include weight gain, fatigue, constipation and depression. It can be treated with replacement doses of thyroid hormones.

"The thyroid is the master gland of metabolism, or energy, and if it's not in balance, it literally can affect every part of your body," Dr. Ordon says.

How to Balance Thyroid Levels • Eat foods high in minerals, such as mixed nuts, cashews, sunflower seeds and yogurt • Eat foods high in zinc such as beef, lamb, pork and salmon

Tongue Lumps If you've ever had small bumps or lumps on your tongue, you know they can be uncomfortable. But are they normal?

"Kids get them a lot from eating too much candy — or so I tell them!" pediatrician Dr. Jim Sears says. "Anybody can get them from eating citrus fruits or strawberries. Sometimes, it kind of makes the tongue a little irritated. They kind of get inflamed for a couple of days ... but they eventually go away. Those are the harmless ones."

If you develop bumps on only one side of your tongue, however, it may be a sign of oral cancer. "You have to watch anything that's going on in your mouth," Dr. Ordon says. "Obviously, pain or anything that's a lump or nodular, you want to be suspicious.

"If you have something going on inside your mouth that doesn't heal in a matter of days, you definitely should have it looked at," Dr. Ordon adds.

Know Your NailsWhen you jam your finger in a door or drop something on it, you expect to see a bruise. But if black or brown streaks develop under your fingernails without any trauma, you should see a doctor right away.

While there is a chance the streaks are harmless, they may be a telltale sign of acral lentiginous melanoma, also known as hidden melanoma. This form of skin cancer only develops under nails, on the palms of the hands, the soles of the feet and on mucous membranes. "This is a killer," Dr. Ordon says. "One of the most serious forms [of the disease]."